Pharm - Lecutre 3 - signal transduction

Question 0

What does cortisol bind to once inside the target cell?

Answer 0

GR = glucocorticoid receptor

Question 1

What carrier protein does cortisol bind to?

Answer 1

CBG

Question 2

How does cortisol get into through the plasma membrane?

Answer 2

diffusion

Question 3

What occurs after GR is bound by cortisol in the cytoplasm?

Answer 3

1) Cortisol causes a conformation change on the GR receptor,

2) This releases inhibitory proteins HSP70. The GR receptor is now free to diffuse into the nucleus

Question 4

What occurs once once the active GR receptor diffuses into the nucleus?

Answer 4

The active receptor binds to a hormone response element (GRE = glucocorticoid response element)

Question 5

What are the subunits of the Nicotinic acetylcholine receptor?

Answer 5

a1, a2, B, y, delta

Question 6

What type of receptor are Nicotinic acetylcholine receptors?

Is this excitatory or inhibitory?

Answer 6

Ion channel-linked receptor

Excitatory

Question 7

Where is the Nicotinic acetylcholine receptor located? (3)

Answer 7

1) Nueromuscular junction
2) peripheral autonomic nervous system
3) central nervous system

Question 8

What type of receptor is the GABA receptor?

Answer 8

gated Cl- channel

Question 9

What type of response is elicited from GABA receptors?

Answer 9

inhibitory - GABA is the main post-synaptic inhibitory transmitter in CNS

Question 10

What affect does the activated GABA receptor have on the cell electrical state?

Answer 10

It allows Cl- and so hyperpolorizes the cell

Question 11

How many times does the GCPR pass through the membrane?

Answer 11

7

Question 12

What are the three subunits of G proteins and what are their function?

Answer 12

Ga: binds GT, binds effectors, acts as GTPase

Gbeta and Ggamma form the beta/gamma dimer and anchors to the membrane

Question 13

What state of the G protein elicits an active response? What turns off this response?

Answer 13

GTP bound to the Galpha subunit occurs when activated

GTPase activity of the alpha subunit converts GTP to GDP and turns activity off

Question 14

What are three types of Galpha proteins and what do they do?

Answer 14

1) Gas (stimulates adenylyl cyclase)
2) Gai (inhibits adenylyl cylcase)
3) Gaq (stimulates phospholipase C)

Question 15

What are two possible structures of Tyrosine Kinase-Linked receptors?

Answer 15

1) single protein with one transmembrane domain

2) tetramer composed of 2 EC subunits and 2 transmembrane subunits

Question 16

Where does the ligand bind a Tyrosine Kinase-Linked receptor?

Answer 16

EC domain

Question 17

What occurs upon ligand binding to the Tyrosine Kinase-Linked receptor? (3)

Answer 17

1) dimerization
2) activation of cross-phosphorylation (the 2 cytoplasmic subunits phosphorylate each other
3) binding of intracellular signaling molecules

Question 18

What are examples of serine/threoinine specific protein kinases? (4)

Answer 18

PKA
PKC
Ca2+/calmodulin dependent protein kinase
MAP kinases

Question 19

What are examples of tyrosine specific protein kinases?

Answer 19

EGF receptor (and other tyrosine kinase-linked receptors)
Src,
Abl

Question 20

What is an example of dual specificity protein kinase? What do these proteins phosphorylate?

Answer 20

Phosphorylate both threonine and tyrosine

MAP kinase kinase (MKK1)

Question 21

What are examples of second messengers?

Answer 21

cAMP
DAG
IP3
Calcium

Question 22

How is cAMP generated?

Answer 22

generated by adenyl cyclase when it is activated by Gas

Question 23

How is DAG and IP3 generated?

Answer 23

Generated when PLC cleaves PIP2 into DAG + IP3

Question 24

What is the signaling pathway for cAMP regulated by GPCRs?

Answer 24

1) ligand binds receptor 2) Gas binds GTP and dissociates from By subunits 3) Gas-GTP activates adenylyl cyclase 4) adenylyl cyclase converts ATP to cAMP 5) cAMP activates PKA 6) PKA phosphorylates and activates or inactivates an enzyme 7) enzyme makes (or stops making) products

Question 25

What is the structure of PKA?

Answer 25

Tetramer - 2 catalytic and 2 regulatory subunits

Question 26

How does PKA become active and what happens? (3 steps)

Answer 26

1) The R subunits each bind a cAMP molecule 2) The R and C subunits dissociate 3) C subunits become autophosphorylated and activated What happens: C subunit phosphorylates proteins on Threonine and serine residues activating or inactivating them

Question 27

What is the difference between Gas activity and Gai? (2)

Answer 27

1) Gas stimulates adenylyl cyclase, Gai inhibits it | 2) they are activated by different GPCR's

Question 28

What inositol-lipid pathway? (5 steps)

Answer 28

1) ligand binds to and activates GPCR 2) Gaq binds GTP and dissociates from By subunits 3) Gaq-GTP activates phospholipase C (PLC) 4) PLC cleaves PIP2 to make DAG and IP3 5a) IP3 diffuses into cytoplasm and releases calcium from ER 5b) DAG remains attached to membrane and together with calcium, activates PKC

Question 29

How are Monomeric G proteins activated?

Answer 29

Monomeric G proteins are recruited to receptor linked-tyrosine kinase and turned on by GEF

Question 30

How are monomeric G proteins turned off?

Answer 30

Monomeric G proteins are recruited to receptor linked-tyrosine kinase and turned off by GAP

Question 31

What type of molecule is RAS?

Answer 31

monomeric G protein

Question 32

What type of molecule is SOS?

Answer 32

GEF

Question 33

How is RAS-GTP activated?

Answer 33

1) a ligand binds the tyrosine kinase receptor causing autophosphorylation 2) the receptor binds an adapter protein called GRB2 3) GRB2 activates Sos 4) Sos (a GEF) activates Ras (a monomeric G protein) 5) The GEF (sos in this case) causes Ras-GDP to release the GDP and bind GTP thus activating it

Question 34

How is Ras-GTP inactivated?

Answer 34

When Ras-GTP interacts with GAP, the GAP induces Ras-GTP's inherent GTPase activity and GTP is hydrolyzed to GDP

Question 35

What activates Raf to begin the MAP Kinase signaling cascade?

Answer 35

Ras-GTP activates Raf

Question 36

What type of molecule is Raf?

Answer 36

a MAP kinase kinase kinase

Question 37

What are the steps for the MAP kinase signaling cascade starting from an activated Ras-GTP?

Answer 37

1) Ras-GTP activates Raf 2) Raf phosphorylates MKK1 3) MKK1 phosphorylates ERK 4) ERK phosphorylates many different transcription factors

Question 38

What type of molecule is MKK1?

Answer 38

MAP Kinase Kinase

Question 39

What type of molecule is ERK?

Answer 39

MAP kinase

Question 40

What type of receptor is the EGF receptor?

Answer 40

Tyrosine kinase receptor

Question 41

What would mutations in EGF receptor cause?

Answer 41

Abnormally high activity of the MAP kinase signaling cascade - promotes tumor growth

Question 42

What would mutations in Ras cause?

Answer 42

Abnormally high activity of the MAP kinase signaling cascade - promotes tumor growth

Question 43

What is the mechanism of gefitinib?

Answer 43

Inhibits signaling of the EGF receptor

Question 44

What is the mechanism of erlotinib?

Answer 44

Inhibits signaling of the EGF receptor

Question 45

What two drugs inhibit signaling of the EGF receptor?

Answer 45

1) gefitinib | 2) erlotinib

Question 46

What determines the efficacy of gefitinib and erlotinib regarding tumor supression?

Answer 46

Efficacy is high if the tumor expresses a MUTATED EGF receptor. They don't work as well (-10%) if the EGF receptor mutations are absent

Question 47

What are mechanisms of adaption? (2)

Answer 47

Receptor mediated endocytosis | Receptor desensitization

Question 48

What is adaption?

Answer 48

Modulation of signals in response to intensity and frequency of stimulation

Question 49

How is receptor mediated endocytosis carried about?

Answer 49

1) upon binding the ligand, receptors migrate to coated pits 2) the receptor is internalized 3) some receptors are recycled, some are degraded by lysosomes

Question 50

What is the role of clathrin?

Answer 50

clathrin is the structural protein that forms the electron dense cage that forms the vesicle that receptors are endocytosed in

Question 51

What is CURL?

Answer 51

the tubular-reticular structure that forms the compartment for receptor-ligand uncoupling

Question 52

What is the p.H. in CURL and why?

Answer 52

4.5 - 5 to favor dissociation of ligand and receptor

Question 53

What is retroendocytosis?

Answer 53

The recycling of endocytosed receptors

Question 54

What is homologous desensitization? What is the process? (2 steps)

Answer 54

The desensitization of the stimulated receptor Process: 1) GPCR is phosphorylated by betaARK 2) beta arrestin binds to phosphorylated GPCR and inactivates it

Question 55

What is Heterologous desensitization? Mechanism?

Answer 55

Both the stimulated and unstimulated receptors are blocked Mechanism: 1) phosphorylation of receptors 2) competition for shared second messengers